The water that carved the channels to the north and east of the Valles Marineris canyon system had tremendous erosive power. One consequence of this erosion was the formation of streamlined islands where the water encountered obstacles along its path. This image shows two streamlined islands that formed as the water was diverted by two 8-10-kilometer-diameter craters lying near the mouth of Ares Vallis in Chryse Planitia. The water flowed from south to north (bottom to top of image). Note that the ejecta blanket of the third large crater (located at the tapered downstream tail of the uppermost island) is uneroded, an indication that this crater formed sometime after the channel was active. The height of the scarp surrounding the upper island is about 400 meters, while the scarp surrounding the southern island is about 600 meters high.
From Mars Digital Image Map, image processing by Brian Fessler, Lunar and Planetary Institute